Warning

This documents an unmaintained version of NetworkX. Please upgrade to a maintained version and see the current NetworkX documentation.

bfs_predecessors

bfs_predecessors(G, source)

Return dictionary of predecessors in breadth-first-search from source.

Parameters:

G : NetworkX graph

source : node, optional

Specify starting node for breadth-first search and return edges in the component reachable from source.

Returns:

pred: dict

A dictionary with nodes as keys and predecessor nodes as values.

Notes

Based on http://www.ics.uci.edu/~eppstein/PADS/BFS.py by D. Eppstein, July 2004.

If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched.

Examples

>>> G = nx.Graph()
>>> G.add_path([0,1,2])
>>> print(nx.bfs_predecessors(G,0))
{1: 0, 2: 1}